[6] On September 9 of that same year, Christie was seriously injured by a crash when his car struck loose debris during a lap at Brunots Island Race Track in Pittsburgh, Pennsylvania.

[4] In a twelve-car endurance race earlier that day, scheduled to run 50 miles, the Haynes car of driver Rex Reinertson had lost its right front tire with disastrous results, catapulting into the air and landing on its roof.

[4] Reinertson was crushed beneath the car, suffering injuries (including a skull fracture) that proved ultimately fatal, and his mechanic Clarence Bastion was ejected from the vehicle and thrown 50 feet (15 m) through the air, breaking both of his arms and both of his legs.

[4] After ten more laps, the race was stopped so that the injured racers could receive medical treatment, and Reinertson's car was cleared off the track.

[4] Doctors who treated Christie expressed concern that he might be crippled as a result of his injuries, or lose the sight of his damaged eye, and news of his accident was kept from his wife, who was herself seriously ill at their home in River Edge, New Jersey.

However, in 1909 designs were less standardized than they would become by 1959, and for Christie the vehicle's more striking novelty was the fact that the entire "forecarriage", incorporating all the major mechanical components, could be detached and replaced in "less than one hour".

Christie had built an amphibious light tank a decade before Donald Roebling's Alligator, and this was to be displayed during the military's Winter Maneuvers of 1924 at Culebra, Puerto Rico.

Despite the fact that the vehicle came ashore after the exercise had been declared officially finished, Cole stated that the tank possessed the capability of being developed into an extremely valuable weapon, especially in association with landing operations.

This reduced space in the interior of the tank, but (combined with a very light overall weight) allowed for unprecedented high-speed cross-country mobility, albeit at the cost of extremely thin armor.

There the Army's Chief of Staff, General Charles P. Summerall, and other high-ranking officers were impressed and strongly recommended that the Infantry Tank Board conduct further, official tests of the new vehicle.

While Christie advocated the use of lightweight tanks with long range and high speed, designed to penetrate enemy lines and attack their infrastructure and logistics capabilities, they considered the tank as simply an auxiliary weapon to help protect the infantry, and to help isolate and reduce enemy strongpoints near the front lines, much as they had been used during the previous world war.

He began discussing his advanced chassis and suspension systems with foreign governments; Poland, the USSR and the United Kingdom had all expressed interest in the designs.

In 1929, Captain Marian Rucinski of the Polish Military Institute of Engineering Research (WIBI) was sent to the US, and soon learned of the M1928 tank being constructed by Christie's company, the US Wheel Track Layer Corporation in Linden, New Jersey.

Rucinski's opinion was so enthusiastic that on February 16, 1930 a special acquisition commission was dispatched to the US, commanded by the Chief of the Engineering Department, Colonel Tadeusz Kossakowski.

Christie later failed to fulfill his contract obligations, and to avoid potential litigation, eventually returned the payment made by the Polish government, which never obtained the tank they had ordered.

[14] Though the USSR did not have diplomatic relations with the US at the time, and was prohibited from obtaining military equipment or weapons, Soviet OGPU agents at the trade front organization AMTORG managed to secure plans and specifications for the Christie M1928 tank chassis in 1930 using a series of deceptions.

[15] The two Christie tanks, documented falsely as agricultural farm tractors, were sold without prior approval of the U.S. Army or Department of State, and were shipped without turrets to the USSR.

Why payment necessary to secure the vehicle was not deducted from this figure is not known but the net cost increased to £10,420 18s 4d, which included British Customs Duty and 'other expenses'.

After the beginning of World War II in 1939 and the US commencement of hostilities in 1941, Christie again submitted tank designs to the army, all of which featured his suspension system and large, convertible road wheels.